General Question

How is cell division possible?

Consider the following engineering problem. You are told to build a machine that can split itself into two copies. If the machine had access to parts outside of itself, I can picture it being able to assemble the parts into a version of itself. But that is not what is happening. It is more like having the machine cannibalize parts of itself to build a scaled down copy while leaving behind a somewhat diminished version of itself. Conceptually, how is such a thing possible?

The only way I can think of it as possible is to imagine that there is enough slop outside of the nucleus of the cell to use as spare parts to construct a second nucleus. Upon division, the two child cells will not have enough excess material to divide again, but will do so after accumulating enough material through growth

8 Answers

It’s not. Cells just lack a brain, and so they don’t realize it’s impossible, and they go no and do it.

Actually, the machine DOES have access to parts outside itself. Because it is so small, it is made of incredibly tiny parts such as hydrogen, carbon, oxygen, nitrogen and other atoms. It has access to a nearly unending supply of these externally. To make a copy of itself, it just needs to take these in, and then use chemical processes to turn them into long chain molecules, which it does all the time as a part of it’s job as a machine.

I agree it’s mind boggling. That is why, I submit, it’s done only by things too little to posses a mind.

It does not have to construct a second nucleus right away.
It just duplicates its genome (cutting up the double helix into 2 strands, those get moved to opposite ends of the cell, then each strand completes itself with manufactured nucleotides, where each nucleotide goes is dictated by the chemical properties of the nucleotides in the already existing strand), then the cell divides by pinching itself in half. Wrap up the new double helixes in membranes and you have a new nucleous, and all is done.
And the cell does have access to “spare parts” from outside, it is the stuff you eat, in molecular form, that gets synthesised into more complex molecules by the cell internal apparatus as needed.

I think your second paragraph is approximately correct. There is enough raw material in the cell for the nucleus to reproduce then form new cell walls. The resulting two cells are each smaller than the original and presumably will enrich themselves before dividing again.

Yeah, cells can’t simply spontaneously divide and do it again and again without growth. Daughter cells need to grow before being capable of dividing again. There’s a huge host of checks and balances in cells (more in eukaryotes like us, but still tons in prokaryotes like E. coli) that keep them from dividing too fast. Speaking of E.coli, despite them being a poster child for fast-dividing cells, they still take around 20 minutes of simply resting and eating before being capable of dividing a second time, and that’s in a very nutrient-rich environment.

Also, you see machines creating new machines inside themselves all the time. Where do you think people come from? That’s pretty much exactly “having the machine cannibalize parts of itself to build a scaled down copy while leaving behind a somewhat diminished version of itself.” Granted, most new mothers would be a little miffed saying they’re ‘diminished’, but technically it’s correct, pregnancy takes a large toll on the body because the fetus is literally feeding off them.